Previous studies have indicated that in all land plants examined to date, the chloroplast gene trnLUAA is interrupted by a single group I intron ranging from 250 to over 1400 bp. The parasitic Epifagus virginiana has lost, however, the entire gene. We report that the intron is missing from the chloroplast genome of two arctic species of the legume genus Hedysarum (H. alpinum, H. boreale). DNA sequencing of the trnL gene and trnL-trnF intergenic spacer (trnL-F), as well as portion of trnF exon in these species confirms the absence of trnL intron and shows that it has been deleted from the gene precisely along established exon/intron splicing sites. Phylogenetic analysis of trnL-F sequence data revealed that they are closely related species. This indicates that the intron was lost from the chloroplast genome before the divergence of the two Hedysarum species. It is concluded that this rare genomic structural mutation may have occurred once during the evolution of land plants.